1. Field of the Invention
The present invention relates to a fuel control system for turbine engines, and in particular to a modular sub-assembly incorporating some of the components of the system.
2. Summary of the prior art
Fuel control systems for turbine plants are known which comprise a flow regulator having its upstream side connected to the output of a proportioning pump and its downstream side to an injection device, a control valve mounted in a by-pass between the pump and the feed regulator, a pressure drop detector intended to provide an output at a modulated pressure Pmod dependent upon the pressure drop Pam-Pav wherein Pam and Pav are the pressures measured upstream and downstream respectively of the flow regulator, the Pmod output acting on the control valve to open or close it when the pressure drop across the flow regulator varies so as to keep the pressure drop substantially constant, an overspeed limiter responsive to the rotational speed of the turbine engine to reduce the injection flow in the user installation when a fixed overspeed threshold is exceeded so as to prevent possible racing of the engine, a stop valve capable of stopping, on command, the flow of fuel injected into the engine, and a control computer for controlling the foregoing components.
In standard control systems the functions of pressure drop detection and overspeed limitation are performed separately by means of independent hydraulic amplifiers constituted by a rotary slide for the pressure drop detector and a servo-valve of the nozzle-vane type for the overspeed limiter. In addition there is a complementary device intended to open the control valve to prevent a burst in the control system when the stop-valve is being closed. Indeed, at that particular moment, the control valve would normally have a tendency to close too, whereas it should be opened widely to by-pass the flow of fuel delivered by the high pressure proportioning pump.